Replaceable printing sleeve

ABSTRACT

A replaceable sleeve having a working surface is provided which is adapted to be mounted on a carrier. The sleeve includes an inner polymeric layer, a reinforcing layer overlying the inner layer, an intermediate polymeric layer overlying the reinforcing layer, and an outer polymeric layer. The sleeve may include a cushion layer between the intermediate layer and the outer layer. The layers comprising the sleeve are formed around a support and then cured simultaneously in a single step. The resulting sleeve may be used in printing operations or in other applications such as coating, embossing, laminating, calendering and the like.

BACKGROUND OF THE INVENTION

The present invention relates to a replaceable sleeve which may bereadily mounted onto a cylindrical carrier, and more particularly, to areplaceable sleeve comprising a multilayer reinforced composite whichmay be cured in a single vulcanizing step.

Rubber-covered cylindrical rollers are widely used in industry for anumber of applications, particularly for web or sheet handling andprocessing applications such as the embossing, calendering, laminating,printing and coating of paper, film, foil, and other materials. Inaddition to their use in web processing equipment, such rubber-coveredrollers are often employed in conveyors and various office machines.Such rollers are typically comprised of a cylindrical (metal) core orother support with an outer covering of rubber, elastomer, or polymermaterial. However, after extended use, the covering on the rollers wearsdown and must be resurfaced or replaced. This typically requires thatthe rollers be sent to an outside source where the old surface is grounddown and a new surface is applied. This is inconvenient and expensive asit requires that the processing equipment be shut down while the rolleris being resurfaced or that the end user stock additional replacementrollers. Even in the latter instance, the rollers must be eventuallysent out for resurfacing.

Cylindrical rollers are widely used in the printing industry. Forexample, printing rollers or sleeves are used in the flexographicprinting industry for providing a mountable surface for flexographicprinting plates. In a typical flexographic printing press, the sleeve ismounted onto a printing cylinder using pressurized air to expand thesleeve, and the printing plates are then attached to the outer surfaceof the sleeve.

While thin metal sleeves for use on printing cylinders have beenemployed in the past, more recently, printing sleeves have beendeveloped which are comprised of polymeric materials. For example,printing sleeves are known which include laminated polymeric layersreinforced with a woven or nonwoven fabric layer. Such sleeves providean advantage over metal rollers in that they are readily expandable formounting on a cylinder, are seamless, and provide good structuralintegrity for printing operations without the damage and safetylimitations of thin metal sleeves. However, such sleeves are typicallyexpensive and slow to fabricate as each component must be formed andcured separately and then assembled or formed into a composite. Further,many polymeric printing sleeves in use require specific polymers and/orcure temperatures, which restricts the choice of materials or propertiesof the finished sleeve surface which may be desired for differentprinting applications.

Accordingly, there is still a need in the art for a replaceable sleevewhich is readily mountable on a cylinder or other carrier, which may befabricated quickly and easily, and which may be used in a wide varietyof applications including printing applications as well as web or sheethandling or and/or processing applications and the like.

SUMMARY OF THE INVENTION

The present invention meets that need by providing a replaceable sleeveadapted to be mounted on a cylindrical carrier which is comprised of amultilayer composite and which may be used in a number of applicationswhich typically utilize polymer covered rolls including but not limitedto web or sheet handling operations and flexographic printingoperations. The sleeve is efficiently produced as the layers comprisingthe sleeve may be cured simultaneously. The sleeve is essentiallyseamless, chemically resistant, and may be easily mounted on a varietyof carriers. When used in printing operations, the sleeve provides highprint quality and performs within the tolerance levels required by theprinting industry.

According to one aspect of the present invention, a replaceable sleeveis provided which is adapted to be mounted on a carrier. By carrier, wemean any structure which functions to support the sleeve during use andallows it to rotate during use including but not limited to cylinders,tubes, and liners. The replaceable sleeve is made up of a combination oflayers including an inner polymeric layer, a reinforcing layer overlyingthe inner layer, an intermediate polymeric layer overlying thereinforcing layer, and an outer polymeric layer forming a workingsurface, where the Shore A hardness of the inner polymeric layer isgenerally equal to or greater than the Shore A hardness of theintermediate and outer polymeric layers. By working surface, we meanthat the outer surface of the sleeve may be adapted for a number of usessuch as printing, embossing, coating, calendering, etc.

Preferably, the inner layer, intermediate layer, and outer layer arecomprised of an elastomeric material selected from, but not limited to,the group consisting of butyl rubber, nitrile rubber, EPDM rubber,natural rubber, synthetic rubber, neoprene rubber, a blend of nitrilerubber and polyvinyl chloride, and polyurethane. Further, the innerlayer, intermediate layer, and outer layer preferably have a Shore Adurometer hardness of from about 30 to 90.

In a preferred embodiment, the inner layer has a Shore A hardness of atleast about 70, and comprises, for example, a carboxylatednitrile-butadiene copolymer. The inner layer enhances the durability ofthe sleeve for repeated usage.

The reinforcing layer is preferably comprised of wound fibers of amaterial selected from the group consisting of polyester, cotton,fiberglass, cotton-wrapped polyester, rayon, carbon filaments, and otherhigh modulus synthetic or organic fibers.

In a preferred embodiment of the invention, the sleeve further includesa cushion layer which may be positioned between the intermediatepolymeric layer and the outer surface layer which functions to provideenergy absorption and resiliency to the sleeve. The cushion layer may becomprised of an open or closed-cell polymeric foam or a polymer layerhaving a Shore A durometer hardness of from about 25 to 55.

The outer polymeric layer functions both as a protective layer for thecushion layer as well as providing a working surface having theparticular characteristics needed for a specific end use. Preferably,each of the layers comprising the sleeve has a thickness of from about0.001 to 0.750 inches (0.0025 cm to 1.905 cm).

The present invention also provides a method of making the replaceablesleeve of the present invention, which comprises the steps of forming aninner layer of a hard polymeric material into a cylindrical shape andmounting the layer on a support. A reinforcing layer is applied over theouter surface of the inner layer, and an intermediate polymeric layer isapplied over the outer surface of the reinforcing layer. An outerpolymeric layer may be applied over the outer surface of theintermediate polymeric layer. The layers are then cured simultaneouslyin a single step to form the sleeve. The layers are preferably cured ata temperature of between about 285° F. to 310° F. (140° C. to 154° C.)and for a time to effect vulcanization of all of the layers.

The method also includes the optional step of applying a cushion layerover the outer surface of the intermediate polymeric layer prior toapplying the outer layer. Where the cushion layer is comprised of anopen or closed-cell polymeric foam, the cellular structure may be formedin a separate step prior to applying the outer layer.

The outer surface of the resulting sleeve may be further processed asdesired to provide a working surface for specific applications. Forexample, the outer layer may be ground to provide a surface roughnesswhich is suitable for applications such as coating, calendering,laminating, and the like, or which may be polished, etched or engravedto provide a surface which may be used for embossing or printing. Thesleeve may be readily mounted and dismounted from a carrier usingpressurized air. In addition to the printing and coating applicationsdescribed above, the sleeve may be used in any other applications whichrequire the use of a polymer covered roller, such as flood/solid colorprint rolls, meter rolls, nip rolls, support rolls, and the like.

Accordingly, it is a feature of the present invention to provide areplaceable sleeve having a working surface which may be readily mountedon a carrier, which is easily fabricated, and which may be used in avariety of applications. This, and other features and advantages of thepresent invention will become apparent from the following detaileddescription, the accompanying drawings, and the appended claims.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1 is a perspective view, partially sectioned, of the replaceablesleeve of the present invention mounted on a printing cylinder;

FIG. 2 is a perspective view of the replaceable sleeve of FIG. 1; and

FIG. 3 is a sectional view taken along lines 2--2 of FIG. 2.

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENT

The replaceable sleeve of the present invention provides severaladvantages over other prior sleeves that are covered with rubber orpolymer in that all of the layers comprising the sleeve are seamless andmay be cured in a single step, which allows the sleeve to be producedmore efficiently. And, because the layers comprising the sleeve are notlimited to the use of specific polymers or curing methods, theproperties of the sleeve may be tailored as desired for specificapplications. For example, where the sleeve is used in printingoperations, the outer layer of the sleeve may be finished so that it canbe used as the printing surface, thus eliminating the requirement forthe attachment of separate printing plates. The sleeve of the presentinvention also offers the advantage that it may be easily replacedon-site without having to shut down processing equipment for extendedperiods of time. That is, when the sleeve surface becomes worn orotherwise needs replacement, the sleeve may be readily dismounted fromits carrier, and a new sleeve quickly mounted in its place.

Referring now to FIGS. 1 and 2, the replaceable sleeve 10 of the presentinvention is shown. As shown in FIG. 1, the sleeve 10 is mounted on aconventional printing cylinder 12. However, it will be apparent to thoseskilled in the art that the sleeve may be adapted to be mounted on avariety of other carriers. In one method, cylinder 12 is hollow and mayinclude an interior chamber (not shown) which is used as a compressedair chamber through which air may be passed for expanding the sleeve 10during mounting and dismounting operations. The cylinder may include aplurality of spaced apart, radially-extending apertures 18 from whichair in the chamber may exit to or which may be used to expand the sleeve10 during mounting and dismounting operations. The air is introducedinto the chamber by an air hose 14 which can communicate with theapertures of the cylinder 12. The sleeve is typically mounted onto thecylinder by introducing air at a pressure of about 80-120 psi (5.6 to8.4 kg/cm²) to expand the sleeve and permit it to be slipped onto thecylinder.

FIG. 3 illustrates the layers comprising sleeve 10 including an innerpolymeric layer 20, a reinforcing layer 22 overlying inner layer 20, anintermediate polymeric layer 24 overlying reinforcing layer 22, and anouter polymeric layer 28. As shown, the sleeve may optionally include acushion layer 26 between outer layer 28 and intermediate layer 24. Anysuitable rubber adhesives 19 may be used to bond the layers togetherduring vulcanization including but not limited to CHEMLOCK, commerciallyavailable from Lord Corporation.

The inner, intermediate, and outer polymeric layers of the sleeve may becomprised of a number of different polymers including butyl rubber, EPDMrubber, nitrile rubber, natural rubber, neoprene rubber, a blend ofnitrile and polyvinyl chloride, polyurethane, and synthetic rubber.Suitable synthetic rubbers include HYPALON, a chlorosulfonatedpolyethylene available from DuPont. Inner polymeric layer 20 ispreferably comprised of a carboxylated nitrile copolymer, which has aShore A durometer hardness of between about 65 to 90 aftervulcanization. The hardness and toughness of the inner layer providesabrasion resistance to the sleeve and forms a sufficiently stablestructure which provides support for the remaining layers of the sleeve.

Reinforcing layer 22 provides additional dimension and support to thesleeve, and is preferably comprised of wound fibers such as polyester,cotton, fiberglass, cotton-wrapped polyester, rayon, carbon filaments,or other high modulus synthetic or organic fibers. Suitable syntheticfibers include aramid fibers available from DuPont under the designationKEVLAR and fiberglass or polyester threads available from a variety ofsources. Preferred for use in the present invention are fiberglassfibers which have been twisted into a cord or thread.

Cushion layer 26 provides cushion to the outer surface layer of thesleeve. In instances where the sleeve is used in printing operations,the cushion layer also provides cushion to the printing plate that maybe adhered to it. The cushion layer typically comprises an open-celledpolymeric foam or a layer of a soft polymer having a Shore A durometerhardness of from about 25 to 55.

In the preferred method of making the sleeve of the present invention,inner polymeric layer 20 is formed by either an extrusion process inwhich the desired polymer is extruded as a cylindrical tube through anextrusion die, or by calendering layers of the polymer onto a mandrel.If the inner layer is formed by extrusion into a tube, it issubsequently mounted onto a mandrel by expansion with blown air. Themandrel is typically cylindrically-shaped and may include a hollowinternal chamber and a plurality of holes on its outer surface to allowthe passage of pressurized air.

After the inner polymeric layer has been mounted or formed on themandrel, it remains in an uncured state. An adhesive is then preferablyapplied to the inner layer to form an adhesive layer 19 prior to theapplication of reinforcing layer 22. The reinforcing layer, whichpreferably comprises fiberglass or polyester twisted cord, is thenapplied to the inner layer 20 by winding under tension and wrappedaround the layer at approximately 20 to 35 threads per linear inch.Another layer of adhesive is then preferably applied over thereinforcing layer.

Intermediate layer 24 may be formed in the same manner as inner layer20, either by extrusion or calendering. If formed by extrusion, theintermediate layer is then mounted by expansion with blown air onto thesleeve over adhesive layer 19.

In embodiments where cushion layer 26 is included in the structure,another layer of adhesive may be applied over the intermediate layerprior to application of the cushion layer. The cushion layer may beformed by conventional means known in the art, and is preferably formedby extruding the desired polymer with chemical blowing agents which areactivated during vulcanization. Suitable chemical blowing agents includemagnesium sulfate, hydrated salts, hydrazides such as p-toluene sulfonylhydrazide and p,poxybisbenzene, sulfonyl hydrazide, and carbonamidessuch as 1,1'-azobisformamide. Nitrate, nitrite, bicarbonate andcarbonate salts may also be used. Alternatively, the cushion layer maybe formed in a separate step as disclosed in commonly-assigned U.S. Pat.No. 4,548,858 to Meadows, the disclosure of which is hereby incorporatedby reference. In another alternative embodiment, the cushion layer maybe formed by mixing a suitable salt such as hydrated magnesium sulfatewith a polymeric material such as rubber and then curing and leachingthe salt out, forming cavities in the rubber. Such a process isdisclosed in commonly assigned U.S. Pat. No. 3,928,521 to Haren et al,the disclosure of which is hereby incorporated by reference. Stillanother method of forming the cushion layer includes the incorporationof microcapsules in an elastomeric matrix and fixing those microcapsulesin a low temperature partial vulcanization step as described in U.S.Pat. No. 4,770,928 to Gaworoski, the disclosure of which is herebyincorporated by reference.

Outer polymeric layer 28 is then formed, either by extrusion orcalendering as described above, and then mounted over the cushion layer.A layer of adhesive may be applied to the cushion layer prior toapplication of the outer layer.

The sleeve assembly is then preferably cured (at a temperature ofbetween about 285° F. to 310° F. (140° C. to 154° C.)), for a timesufficient to completely vulcanize each layer in the sleeve in a singlestep. For sleeves of relatively small dimension, a curing time of onlyabout 45 minutes may be needed, while for larger sleeves, a curing timeof more than 6 hours may be required. This flexibility provides anadvantage over previous methods which require the same amount of curingtime regardless of the size of the sleeve.

It should be appreciated that while the sleeve described hereinpreferably includes inner, intermediate, and outer polymeric layers aswell as a reinforcing layer and optional cushion layer, the sleeve mayalso be constructed so that it comprises only the inner layer, or onlythe inner layer, reinforcing layer, and intermediate layer. The sleevemay also be fabricated to include only the inner layer, reinforcinglayer, intermediate layer and cushion layer. Other variations of thelayers comprising the sleeve are possible and within the scope of theinvention, as long as the sleeve includes the inner hard polymericlayer.

The outer surface of the cured sleeve may then be finished as desired byconventional means such as grinding and polishing to provide propersurface conditions for printing or other applications. In printingoperations where printing plates are to be mounted on the sleeve, thesurface is preferably ground so as to achieve a surface roughness ofabout 20 to 100 microinches (5×10⁻⁵ cm to 2.5×10⁻⁵ cm). If the outersurface layer of the sleeve is to be used as a printing surface, thesleeve is preferably super polished to provide a finish of from about 5to 35 microinches (1.25×10⁻⁵ cm to 8.9×10⁻⁵ cm). The resulting sleeve iscapable of meeting tolerances required in the printing industry.

For other applications, the outer surface of the sleeve may further bemechanically or chemically etched or laser engraved to provide asuitable surface for transferring ink images onto a substrate, or forother uses such as texturing, embossing, coating etc. It should beappreciated that the properties of the sleeve may be tailored as desiredby modifying the materials used for each layer, as well as by modifyingthe layer thickness and curing method.

The sleeve of the present invention can be readily mounted onto ordismounted from any typical carrier such as cylinders, tubes, liners,etc. In addition to printing operations, the sleeve of the presentinvention may be used for any other applications which typically utilizea polymer covered roll including coating, tinting, embossing,laminating, impression, nip, and backup rolls.

While certain representative embodiments and details have been shown forpurposes of illustrating the invention, it will be apparent to thoseskilled in the art that various changes in the methods and apparatusdisclosed herein may be made without departing from the scope of theinvention, which is defined in the appended claims.

What is claimed is:
 1. A replaceable sleeve adapted to be mounted on acarrier comprising:a) an inner polymeric layer b) a reinforcing layercomprised of fibers overlying said inner layer; c) an intermediatepolymeric layer overlying said reinforcing layer; d) a cushion layeroverlying said intermediate polymeric layer; and d) an outer polymericlayer forming a working surface; wherein said inner polymeric layer hasa Shore A hardness which is equal to or greater than the Shore Ahardness of said intermediate and outer polymeric layers.
 2. Thereplaceable sleeve of claim 1 in which said layers have been curedsimultaneously.
 3. The replaceable sleeve of claim 1 wherein said sleeveis seamless.
 4. The replaceable sleeve of claim 1 in which said innerlayer, said intermediate layer, and said outer layer are comprised ofmaterials selected from the group consisting of butyl rubber, nitrilerubber, EPDM rubber, natural rubber, synthetic rubber, neoprene rubber,blends of nitrile rubber and polyvinyl chloride, and polyurethane. 5.The replaceable sleeve of claim 1 in which said inner layer comprises acarboxylated nitrile-butadiene copolymer.
 6. The replaceable sleeve ofclaim 1 in which said inner layer, said intermediate layer and saidouter layer have a Shore A durometer hardness of from about 20 to
 90. 7.The replaceable sleeve of claim 1 in which said inner layer has a ShoreA durometer hardness of at least about
 70. 8. The replaceable sleeve ofclaim 1 in which said reinforcing layer is comprised of a materialselected from the group consisting of polyester, cotton, fiberglass,cotton-wrapped polyester, rayon, carbon filaments, and other syntheticor organic fibers.
 9. The replaceable sleeve of claim 1 in which saidcushion layer comprises an open or closed-cell polymeric foam.
 10. Thereplaceable sleeve of claim 1 in which said cushion layer comprises apolymer having a Shore A durometer hardness of from about 25 to
 45. 11.The replaceable sleeve of claim 1 in which each of said layers has athickness of from about 0.005 to 0.750 inches.